Conceitos e importância da modelagem matemática de qualidade da água para gestão dos recursos hídricosConcepts and importance of mathematical modeling of water quality for water resources management

O acelerado desenvolvimento das atividades humanas, aliado aos impactos causados ao meio ambiente e à pressão pela preservação dos recursos naturais, evidencia a necessidade da busca constante por novas ferramentas de apoio ao processo de tomada de decisões pelo poder público. Dentre as várias ferramentas desenvolvidas ao longo dos anos, os modelos matemáticos de qualidade da água merecem especial destaque e são amplamente encontrados na literatura nacional e internacional, como técnicas eficientes de apoio à gestão dos recursos hídricos. Partindo dessas premissas, o presente artigo tem como objetivo apresentar uma revisão bibliográfica sobre a utilização de modelos matemáticos de qualidade da água, com enfoque aos principais conceitos e modelos relacionados. A modelagem matemática possibilita gerar cenários futuros, estimando custos e, principalmente, as principais medidas preventivas a serem tomadas na execução das atividades humanas. Sendo assim, existe a necessidade de estudos constantes, a fim de diminuir as limitações da aplicabilidade dos modelos de qualidade da água como forma de atender à legislação vigente.AbstractThe accelerated development of human activities, associated with the impacts caused to the environment and to the pressure by preservation of natural resources, highlights the need for the constant search for new tools to support the process of decision making by the government. Among the various tools developed over the years, the mathematical models of water quality deserve special attention, and are found widely in national and international literature as efficient techniques to support the management of water resources. Based on these premises, this paper aims to present a bibliographic review on the use of mathematical models of water quality, with focus on the main concepts and models related. The mathematical modeling allows generating future scenarios, estimating costs and, especially, the main preventive measures to be taken in the execution of human activities. Thus, there is a constant need for studies to decrease the limitations of the applicability of the models of water quality in order to meet current legislation

Effect of different inoculations on biogas and methane production through anaerobia biodigeston using residues from the avícola sector

The present study aimed to analyze the use of different digestates as inocula for the anaerobic digestion of poultry litter, evaluating the biogas and methane production. The inocula used were: bovine and porcine biofertilizer; with feeding loads of 0.67, 1.00 and 1.67 gVS L-1 day-1. Statistical analyses followed a split-plot design, where the main plot being inoculum and the feeding load as secondary. The experimental data were submitted to analysis of variance, at the level of 5% of significance. The following variable responses were considered: biogas production, specific biogas production as a function of volatile solids (VS) added to the biodigester, specific biogas production as a function of organic load, in terms of COD, and methane production. The highest rates of average biogas production, specific biogas production by VS added, specific production of biogas as a function of COD, and average methane production occurred with the use of bovine inoculum. Through the analysis of the total average percentage of methane production, productions of 63.0% and 54.5% for bovine and swine inoculum. Considering the results obtained, the use of bovine inoculum for the process of anaerobic digestion of poultry litter is recommended vinculado a produção de biogás e metano

TDR probes calibration in laboratory conditions

Among the indirect methods to evaluate the volumetric soil water content (?v), the Time Domain Reflectometry (TDR) technique is receiving growing attention. As any technique, it presents advantages and disadvantages: the most serious disadvantage is the calibration necessity. At the present study, values of apparent dielectric constant (Ka) and volumetric water content (?v) for a Red Latosol were obtained in a laboratory experiment, using seventeen probes of TDR, from which two were original and fifteen were manufactured by the staff. This study aimed: a) to calibrate the seventeen probes, in laboratory conditions, comparing six regression models for each probe; b) to verify the viability to use the manufactured probes. It was found out that the best regression model was the cubic polynomial model and that the manufactured probes presented performances comparable to the original ones

Spatial variability of soil physical attributes and its effects on wheat yield / <br> Variabilidade espacial de atributos físicos do solo e seus efeitos sobre a produtividade do trigo

The objective of this paper was to study the spatial variability influence of soil physical attributes in wheat yield. The geostatistics techniques used were semivariogram and contour maps produced by interpolation through usual kriging representing the spatial variability of the soil physical attributes: soil water content, soil total porosity, soil compaction degree and soil resistance to penetration.. Experimental data were at a Rhodic Ferralsol from the Agricultural Engineering Experimental Nucleus at UNIOESTE – Cascavel Campus. Soil physical attributes and wheat yield maps presented a variability standard regarding distribution in experimental area, showing low wheat yield where there was high soil compaction degree, low soil total porosity and low soil water content also presenting good wheat yield where low and medium soil resistance to penetration, medium and high soil water content and low soil compaction degree occurred. Among the studied soil physical attributes studied, soil resistance to penetration was the best attribute in correlation with wheat yield. The second best attribute was soil compaction degree. This paper enabled us to understand in a better way the spatial dependence structure of the studied attributes, as well as the concepts and geostatistics applications.<p><p>Este trabalho teve como objetivo estudar a influência da variabilidade espacial dos atributos físicos do solo sobre a produtividade de trigo. Foram utilizadas técnicas de geoestatística como a construção de semivariogramas e confecção de mapas temáticos, produzidos por interpolação por krigagem de atributos físicos do solo, tais como: conteúdo gravimétrico de água no solo, porosidade total, grau de compactação e resistência do solo à penetração. Os dados experimentais foram obtidos em uma área de Latossolo Vermelho-Escuro, pertencente ao Núcleo Experimental de Engenharia Agrícola da Universidade Estadual do Oeste do Paraná – Campus de Cascavel. Os mapas dos atributos físicos do solo e da produtividade de trigo apresentaram um padrão de variabilidade, mostrando baixa produtividade nos locais de alto grau de compactação, baixa porosidade total e baixo conteúdo gravimétrico de água no solo e apresentando boa produtividade nos locais de baixa e média resistência do solo à penetração, médio e alto conteúdo de água no solo e baixo grau de compactação. Dentre os atributos físicos do solo estudados, a resistência do solo à penetração foi o atributo que melhor se correlacionou com a produtividade do trigo. Este trabalho possibilitou entender melhor a estrutura de dependência espacial das variáveis estudadas, bem com os conceitos e aplicação da Geoestatística

Optimization of nitrogen and phosphorus removal from pig slaughterhouse and packing plant wastewater through electrocoagulation in a batch reactor

This work evaluated the removal of total Kjeldahl nitrogen (TKN) and total phosphorus (P) through electrocoagulation and used aluminum electrodes to optimize the potential differential (pd) and hydraulic retention time (HRT) variables in a batch reactor. The experimental design used was Rotatable Central Composite Design (RCCD). The application of the electrocoagulation in the treatment of effluents from pig slaughterhouses and packing plants proved to be efficient in relation to the removal of TKN and total phosphorus, obtaining maximum efficiency equal to 67.15% and 99%, respectively. The maximum TKN removal value was found in Test 12, where treatment conditions were 30 minutes for HRT and 20 volts for pd, which corresponds to 0.86 A of electric current and a current density of 17.2 mA cm-2. For P, the only test that removed below 99% was the first. Through statistical analyses, it was only possible to obtain a mathematical model for TKN removal. While the response surface graph did not present a defined range of the best conditions for the independent variables, it was possible to observe the tendency for better removal, a wide range of pd and values over 30 minutes for retention time